I. Field
The following description relates generally to wireless communications, and more particularly to a repeater in a time-division duplex (TDD) environment.
II. Background
In the not too distant past mobile communication devices in general, and mobile telephones in particular, were luxury items only affordable to those with substantial income. Further, these mobile telephones were significant in size, rendering them inconvenient for extended portability. For example, in contrast to today's mobile telephones (and other mobile communication devices), mobile telephones of the recent past could not be placed into a user's pocket or handbag without causing extreme discomfort. In addition to deficiencies associated with mobile telephones, wireless communications networks that provided services for such telephones were unreliable, covered insufficient geographical areas, were associated with inadequate bandwidth, and were associated with various other deficiencies.
In contrast to the above-described mobile telephones, mobile telephones and other devices that utilize wireless networks are now commonplace. Today's mobile telephones are extremely portable and inexpensive. For example, a typical modern mobile telephone can easily be placed in a handbag without a user thereof noticing existence of the telephone. Furthermore, wireless service providers often offer sophisticated mobile telephones at no cost to persons who subscribe to their wireless service. Numerous towers that transmit and/or relay wireless communications have been constructed over the last several years, thus providing wireless coverage to significant portions of the United States (as well as several other countries). Accordingly, millions (if not billions) of individuals own and utilize mobile telephones.
The aforementioned technological advancements are not limited solely to mobile telephones, as data other than voice data can be received and transmitted by devices equipped with wireless communication hardware and software. For instance, several major metropolitan areas have implemented or are planning to implement citywide wireless networks, thereby enabling devices with wireless capabilities to access a network (e.g., the Internet) and interact with data resident upon such network. Moreover, data can be exchanged between two or more devices by way of a wireless network. Given continuing advancement in technology, a number of users, devices, and data types exchanged wirelessly can be expected to continue to increase at a rapid rate.
Time division duplex (TDD) is one exemplary protocol that is currently utilized in wireless environments to transmit and receive voice communications and other data. Bi-directional communications between a user terminal and a base station occur within TDD systems over a same frequency during disparate time slots (e.g., an RF channel center frequency is substantially similar in a forward and reverse link). More specifically, when the base station is delivering data to the user terminal, the user terminal listens and does not communicate with the base station. Similarly, when the user terminal is delivering data to the base station, the base station listens and does not attempt to deliver data to the user terminal. Thus, in TDD systems, a user terminal and a base station do not simultaneously deliver data to one another over a same frequency.
In some wireless protocols, wireless repeaters are employed between mobile communication units (e.g., cellular phones, personal digital assistants, . . . ) and base stations to extend communication range there between. Repeaters receive signals between a base station and a user terminal, amplify the received signals, and re-transmit such signals. Repeaters can be employed to provide communication service to a coverage hole, which was previously not serviced by the base station. Repeaters can also augment coverage area of a sector by shifting the location of a coverage area or altering shape of the coverage area. Accordingly, repeaters are often highly desirably for utilization in wireless communications environments.
Various difficulties exist, however, with respect to utilizing repeaters within TDD systems. In particular, continuously amplifying signals in both directions in TDD systems would cause the repeater to oscillate; thus, the repeater would fail to amplify an intended signal and create interference within a wireless system. Without aid of repeaters, however, potential of TDD systems cannot be fully reached.